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A Dummy Chassis For an Atlas C-628 or C-630 Shell Part 3

This weekend I was at the Gosport American Model Railroad Group’s running meet and we set up several layouts including most of our N scale modular layout, Solent Summit. This gave me the perfect opportunity to test out my new 3D printed chassis and trucks for my spare Atlas C-628 shells.

The new chassis, as pictured below, has been designed to fit under either a C-628 or C-630 shell made by Atlas. I now have a few of these spare as the powered chassis have been used for my 3D printed Baldwin DT6-6-2000 and RT-624 (DT6-6-2400) shells.

I also designed the chassis so it could be used as a simple dummy without any working light or electrics. Alternatively it could be used with custom power pickups to supply the original lighting board or maybe a sound decoder. The power pickups, as shown below, are axle wipers and are made from 1mm wide phosphor bronze strips. They fit into the groves and guides printed into the underside of the trucks.

In addition to the axle wipers a circuit board mount has been 3D printed to hold the original circuit board in the correct place. This are the white parts you can see in the first two photos above and they fix into the chassis using sprung hooks. There are holes in the chassis at the hook locations so the parts can be removed by pushing the hooks from the other side with a small screwdriver.

The chassis shown above is the third version I have developed. For the first I used parts that I had already drawn for another dummy chassis but this put the bolster pin, which is the swivel point of the truck, in the wrong location. This meant as the chassis tried to negotiate corners the trucks swung out too far and fouled on parts of the shell which hang down beside the trucks.

The second version was reconfigured to put the bolster pin in the correct place but although the trucks now rotate correctly the brake pistons, protruding from the cylinders on the side of the trucks, were ever-so-slightly too long. These also fouled on the hanging parts of the shell on tight corners.

With the third version all the issues have been fixed and below is a trio of Alco C-628 locomotives. Two of them are dummys; can you tell which ones?

The Southern Pacific Loco, No 7102 on the left is a dummy, but what about the other two?

The Monon locomotive on the right is the dummy. The only visible difference is the colour of the trucks; I painted the dummy trucks with a silver instead of a gray, but with a light weathering on both of them they will become almost identical.

The SP Loco No 7102 is fitted with the circuit board mount and the original circuit board. Our N Scale layout, Solent Summit, is a DCC (Digital Command Control) layout and as such the track is powered with 16v AC. This means that both front and rear lights on the dummy locomotive will be on at the same time as shown below. On a DC (Direct Current) layout the lights will only come on in the direction of travel as normal. The Monon locomotive behind SP 7102 is fitted with a DCC decoder and is currently set to the forward direction with the lights on.

For most of the day I only ran the pair of Monon C-628 locomotives with the powered locomotive in front and the dummy behind. Below is a short video of the pair running through Priddys Yard, past Ted’s Farm and into Solent Summit station. As you can see the dummy unit has no issues with the curves or drag though the couplings from the train. The slight hesitation is due to a short elsewhere on the layout, the dummy loco was not phased by the jolt.

In Solent Summit the pair did some switching, and here you can see the dummy being propelled through the crossovers without any issues.

Here is another short video of the train leaving Solent Summit.

This dummy locomotive is ideal for mid train helpers, rear pusher service or for simply adding to your locomotive roster by saving your spare C-628 or C-630 shells.

A small bit of trivia: The Monon Railroad ran through the state of Indiana before it was incorporated in CSX Railroad. The Monon line actually passed through a town called Gosport at Gosport Junction so running them at the Gosport American Model Railroad Group’s running meet seemed very appropriate, even if it was in the UK.

In a future post I will share with you some videos of dummy units working as mid train helpers & rear pusher on much longer trains.